@xMarvin732
Solved! Thank you!

After the most recent Opera update, the background color of the YouTube video player has changed from black to white, even though dark mode is enabled on both Opera and YouTube. This makes the video interface hard to view and visually unpleasant.

I want to emphasize that I’m not using forced dark mode — just the standard dark mode settings in both Opera and YouTube. I've encountered a similar issue in the past only when forced dark mode was on, but that’s not the case here.

Please investigate this, as it significantly affects the viewing experience.

Thank you,